Genuinely concerned how much reach do the TRAs have.
So this isn't "another trans thread", but you have leapt to the conclusion that the only possible people who might complain about transphobia are TRA's. Yeah, right.
For the record, (and I am not a TRA, nor am I trans) as a manager, if someone reports any offensive or abusive behaviour by someone else, whoever the complainant or the accused, then I carefully investigate the circumstances of that complaint and come to a conclusion and an outcome within the grievance and disciplinary polices as laid down by my employer. Every grievance or disciplinary, no matter what it is about, arises from a specific set of circumstances, and I would take everything into account. I do not have, not do my employers (public sector) any "pre-decided" answers. That would be entirely wrong.
In this set of circumstances, for example, I would consider that you deliberately went out of your way to provoke a specific response whilst denying it was your intention. Similar to the "I'm not a racist but..." defence. At the very least you would get some words of wisdom about not being deliberately goading, and how your actions impact on others and reflect on your employer. Does that help? Not that you care, because that isn't the point, is it?